The following studies will be conducted in the year 06/01/76 through 06/01/77: 1) The relationship between metabolic, histological and external signs of deficiency in rapidly induced vitamin A deficiency. Changes in steady state metabolite and amino acid levels will be correlated with signs of vitamin A deficiency. Labeled compounds will be employed to determine the origin amd fate of compounds whose steady state levels are changed in vitamin A deficiency. 2) Abnormal metabolites associated with vitamin A deficiency. Abnormal compounds associated with the onset of deficiency will be identified and quantitated. The possibility of a clinical test for vitamin A deficiency will be investigated. 3) Receptor sites for RBP-vitamin A complex and vitamin A. Preformed RBP-11, 12, H3 retinol complex and labeled retinol will be injected into deficient rats and the fate of the label determined. Any "receptor" proteins obtained with the proteins obtained after cell homogenates are incubated in vitro with labeled retinol. 4) Vitamin A status and mucopolysaccharide synthesis. Immunofluorescent studies and H3-thymidine pulse labeling of goblet cells will be conducted to better determine whether vitamin A affects glycoprotein synthesis directly, or the rate of differentiation and migration of goblet cells. 5) Immune responses in vitamin A deficiency: Local and systemic immune responses will be studied, with emphasis on the possible role of secretory IgA, rate of synthesis of antibodies in response to DNP-BGG, and association constants (Ko) of the antibodies formed. BIBLIOGRAPHIC REFERENCES: Rojanapo, W., Lamb, A.J. and Olson, J.A. Localization of vitamin A sensitive glycoprotein in rat small intestine. Abstract. Bangkok Symposium on Scientific Research, Mahidol University, Bangkok, Thailand, pg. 109(1975). Madjid, B., Sirisinha, S. and Lamb, A.J. Complement level in vitamin A deficient rats. Abstract, Bangkok Symposium on Scientific Research, Mahidol University, Bangkok, Thailand, pg 110(1975).